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Date:   Fri, 24 Nov 2023 18:23:16 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Thomas Pfaff <tpfaff@pcs.com>
Cc:     ludovic.desroches@microchip.com, tudor.ambarus@microchip.com,
        nicolas.ferre@microchip.com, linux-arm-kernel@lists.infradead.org,
        dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 1/2 stable-6.1] dmaengine: at_hdmac: get next dma
 transfer from the right list
Message-ID: <ZWCcvK5L9vHwSfb2@matsya>
References: <15c92c2f-71e7-f4fd-b90b-412ab53e5a25@pcs.com>
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In-Reply-To: <15c92c2f-71e7-f4fd-b90b-412ab53e5a25@pcs.com>
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On 14-11-23, 13:22, Thomas Pfaff wrote:
> From: Thomas Pfaff <tpfaff@pcs.com>
> 
> In kernel 6.1, atc_advance_work and atc_handle_error are checking for the 
> next dma transfer inside active list, but the descriptor is taken from the 
> queue instead.

Sorry that is not how this works. Please send the patch for mainline and
add a stable tag to the patches. They will be backported to stable
kernels

Also, your patch threading is broken, they appear disjoint and not as a
series

Thanks

> 
> Signed-off-by: Thomas Pfaff <tpfaff@pcs.com>
> ---
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 858bd64f1313..68c1bfbefc5c 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -490,6 +490,27 @@ atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc)
>  	}
>  }
>  
> +/**
> + * atc_start_next - start next pending transaction if any
> + * @atchan: channel where the transaction ended
> + *
> + * Called with atchan->lock held
> + */
> +static void atc_start_next(struct at_dma_chan *atchan)
> +{
> +	struct at_desc *desc = NULL;
> +
> +	if (!list_empty(&atchan->active_list))
> +		desc = atc_first_active(atchan);
> +	else if (!list_empty(&atchan->queue)) {
> +		desc = atc_first_queued(atchan);
> +		list_move_tail(&desc->desc_node, &atchan->active_list);
> +	}
> +
> +	if (desc)
> +		atc_dostart(atchan, desc);
> +}
> +
>  /**
>   * atc_advance_work - at the end of a transaction, move forward
>   * @atchan: channel where the transaction ended
> @@ -513,11 +534,7 @@ static void atc_advance_work(struct at_dma_chan *atchan)
>  
>  	/* advance work */
>  	spin_lock_irqsave(&atchan->lock, flags);
> -	if (!list_empty(&atchan->active_list)) {
> -		desc = atc_first_queued(atchan);
> -		list_move_tail(&desc->desc_node, &atchan->active_list);
> -		atc_dostart(atchan, desc);
> -	}
> +	atc_start_next(atchan);
>  	spin_unlock_irqrestore(&atchan->lock, flags);
>  }
>  
> @@ -529,7 +546,6 @@ static void atc_advance_work(struct at_dma_chan *atchan)
>  static void atc_handle_error(struct at_dma_chan *atchan)
>  {
>  	struct at_desc *bad_desc;
> -	struct at_desc *desc;
>  	struct at_desc *child;
>  	unsigned long flags;
>  
> @@ -543,11 +559,7 @@ static void atc_handle_error(struct at_dma_chan *atchan)
>  	list_del_init(&bad_desc->desc_node);
>  
>  	/* Try to restart the controller */
> -	if (!list_empty(&atchan->active_list)) {
> -		desc = atc_first_queued(atchan);
> -		list_move_tail(&desc->desc_node, &atchan->active_list);
> -		atc_dostart(atchan, desc);
> -	}
> +	atc_start_next(atchan);
>  
>  	/*
>  	 * KERN_CRITICAL may seem harsh, but since this only happens
> 

-- 
~Vinod